The trucking industry has a lot at stake in the pending renewal of U.S. highway legislation. But one thing it is not seeking is lifting the nationwide ban on increases in truck size and weights.

''Any major expansion of LCVs or triple trucks, politically, just isn't going to happen because the public doesn't like them,'' Ed Emmett, president of the National Industrial Transportation League, told a Capitol Hill legislative conference sponsored by Traffic World magazine last week.Nevertheless, shippers are looking for a realistic approach soon to solving legitimate and increasing needs for more trucking capacity.

''If you don't increase weights in the areas where it's appropriate, you are going to have more trucks on the road. And it's statistically provable that you are going have more accidents,'' Mr. Emmett said.

The American Trucking Associations is not pressing the issue of truck sizes this year, but is gearing up to tackle the emotional issue down the road.

''ATA is not currently seeking any changes to the law on truck size and weight. We are not asking for any expansion of the use of triples,'' said Walter McCormick, the ATA's president.

Instead, the ATA, which already has a range of favorable provisions in the legislation, is pushing Congress to adopt a ban on the use of global positioning satellite data by highway enforcement officials.

Mr. McCormick also castigated the railroad industry for continuing to fund, through intermediaries, highway safety groups like Citizens for Reliable and Safe Highways that vehemently oppose any expansion of truck size and weight.

The 1991 highway bill had imposed a nationwide freeze on state laws that govern the size and weight of trucks. Twenty states allow larger combination vehicles. Some also allow triples. ''Railroads need to learn to measure delivery times in minutes, not days,'' Mr. McCormick said.

Instead they are spending millions to fight truckers' efforts to ease federal restrictions, he said.

Railroads have been arguing against new competition proposals claiming they must continue to have regulatory protection.

Meanwhile, the Department of Transportation is conducting a comprehensive study of the issues surrounding proposals to increase truck sizes. A report is due soon.